It is known to feed a person (hereinafter referred to as the “patient”), who has a reduced oral intake function as a result of aging or disease, with a liquid chemical or liquid nourishment in the form of a high-calorie transfusion through a blood vessel by means of a catheter. In some cases, for example as known from JP-U-51 108 389, the position of the catheter in the patient can be confirmed by incorporating an X-ray opaque material in the catheter body. Such a catheter is made of a flexible plastic tube with a portion of the tube incorporating an X-ray opaque material which extends around a circumferential portion of a wall of the plastic tube and also extends in an axial direction of the plastic tube. Consequently, when the catheter remains in a blood vessel of the patient, the position of the catheter can be confirmed using X-rays to identify the portion of the plastic tube containing the X-ray opaque material.
Polyurethane is generally used as the material for making such a catheter because it is strong and bio-compatible (by which it is meant that the material becomes soft in the body or is harmless to the body). More particularly, the polyurethane used in the catheter may be aliphatic polyurethane manufactured from aliphatic isocyanate or aromatic polyurethane manufactured from aromatic isocyanate. Of these, a catheter made from aliphatic polyurethane has excellent workability and bio-compatibility and softens when left in the body.
A catheter made of aliphatic polyurethane is hard when inserted into the body so that it is easy to insert, and becomes soft after it has been left in the body so that it has ideal operability and bio-compatibility. On the other hand, however, a catheter made of aliphatic polyurethane has lower chemical resistance so that it readily degrades when it contacts liquid chemicals. In recent years, anticancer medicines containing alcohol are frequently administered in the form of liquid chemicals with the result that catheters made of aliphatic polyurethane are not suitable in such situations.
On the other hand, a catheter made of aromatic polyurethane has excellent chemical resistance but has the disadvantages that it does not become soft after it has been left in the body, and that it does not blend as effectively with the X-ray opaque material. Consequently, only a small amount of X-ray opaque material can be mixed with aromatic polyurethane with the result that the catheter is difficult to identify by linear contrast radiography. As a result, when a catheter is made of aromatic polyurethane no transparent portion is formed in the catheter and the entire catheter incorporates the X-ray opaque material in order to be able to identify the catheter by linear contrast radiography. Because the catheter is not transparent, this gives rise to a problem in that the passage of the liquid chemical through the catheter cannot be confirmed.